This paper investigates the formation control problem of multiple unmanned aerial vehicles (UAVs) with limited communication in a known and realistic obstacle-laden environment. In order to deal with the limited communication constraints, the leader–follower strategy and the virtual leader strategy are integrated into an optimal control framework to formulate this formation control problem. This combination formation framework can be achieved by integrating a redefined directed graph and a proposed information vector. In more practical applications, an obstacle/collision avoidance strategy is achieved by constructing a non-quadratic cost function innovatively using a virtual flow field approach. The proposed optimal control laws, which derive from the local information rather than the global information, are proved to guarantee the stability of the close-loop system by an inverse optimal control approach. The simulation results demonstrate the effectiveness of the formation flight of multiple UAVs with limited communication in an obstacle-laden environment.
This paper addresses issues related to robust control for an airbreathing hypersonic flight vehicle. Owing to aero-propulsion couplings caused by the unique structure shape, the model of the vehicle is greatly nonlinear and complex, which presents an enormous technical challenge for control. The nonlinear model is transformed into a linear fractional transformation (LFT) model, and a robust gain-scheduling controller based on linear parameter-varying control (LPV) with full block multipliers is obtained. Simulations illustrate great improvements of the dynamic performance in closed-loop system.
Natural flyers and man-made MAVs generally use multiple flapping wing configurations. To understand the aerodynamic performance, three different flapping configurations: single wing, tandem wings, and biplane wings are numerically simulated by a URANS solver coupled with an overset grid method. Moreover, effect of kinematics including oscillating frequency, angle of attack and wing to tail distance are detailed investigated. Results show that the wing-tail interaction significantly benefits the thrust generation when the wings are tandem arranged. Additionally, the tandem arrangement is the most efficiency configuration when applied with high frequencies.Biplane wings model has the most inefficiency propulsive performance, nevertheless it can provide an extensive aerodynamic force. With the increasing AOA, biplane has the largest critical angle from thrust to drag. Wing-tail interaction becomes weaker when the tail is mounted further from the flapping wings. The present of the tail in tandem model bring more benefits compared with the tail in biplane model. The tail in biplane model is only functional for flight control when applied with a non-zero angle of attack.
Because of the high speed, strong coupling between aerodynamics and propulsion system, complex environmental conditions and new propulsion system, the airbreathing hypersonic vehicles have a complex dynamics characteristic. This paper use the generic hypersonic vehicle model (CSULA-GHV) to research this issue. The nonlinear longitudinal equations of motion are linearized based on the assumption of little perturbation. Analyze the dynamic characteristic on a feature point selected. The results show that, the stability of this model is poor. It has to design an efficient controller to adjust the poor stability.
Abstract. Flexibility of an insect wing has an important effect on the aerodynamic characteristics. In this paper, deformations and aerodynamic characteristics of flexible flapping wings referred to a real cicada's wing are investigated. Firstly, 3 flexible flapping wing models referred to a real cicada's wing are established. Then, a method of fluid-structure coupling for flexible flapping wings is studied in ANSYS. Finally, deformations as well as lift & drag characteristics of the 3 flexible flapping wings are simulated with the method of fluid-structure coupling. The result indicates that deformations of flexible flapping wings can enhance the aerodynamic performances, and the model whose flexibility is similar to that of a real cicada's wing has better aerodynamic characteristics.
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